I've (29m) been with my girlfriend (34f) for 3 years. It's been difficult at some points but we've reached a point where we communicate really well and the relationship is going great. We go on dates, spend quality time together, have sex almost everyday.

We've sometimes talked over the years about opening up the relationship a little at some point if we felt like we needed to. I was completely okay with that and to be honest, it kinda turned me on to think of her with someone else. Last year, she even told me there was a mutual attraction between her and a coworker and I asked if she wanted to explore that connection, but she said no.

Well, two weeks ago she told me there is another guy (26m) she met with whom there is mutual attraction and she asked if I would be okay with her going to grab a drink with him. I said yes.

We discussed what we wanted from this. She said she didn't want polyamory and that she had absolutely no feelings towards other people - that I was the one for her, that she wanted to spend her life with me, but that she needed freedom and trust. She also said it wouldn't be a constant thing, that right now she feels like she needs this but she knows it won't last long. I asked her why she felt this need so I could understand better. Essentially, she said :

1. She's scared that she's getting old and wants to know that she's still got it
2. She wants to feel free, like she's her own person and can make her own decisions
3. She has had bad relationships in the past and has trauma related to people trying to control her body. She feels like this would help her heal these wounds.

I feel like in theory, these are all valid and I understand them. But since we've started this, I've been feeling really anxious. They haven't had sex yet, only kissing, but there's this pit in my stomach. Sometimes my mind takes over the anxiety and I can intellectualize it, you know? Like I can remind myself that she loves me, that this doesn't mean anything, that she'll feel better and we'll be a stronger couple afterwards. But most of the time the anxiety is so strong, I can't process it.

I feel so dumb for feeling like this. I don't understand how this went from turning me on to being this painful. She sees that it's making me suffer, but I don't want to go back. I don't want to ask her to suppress and deny these feelings she has. I don't want to be yet another guy telling her what she can or can't do with her body. I want her to be happy, to feel free, to know I trust her completely. I've talked to her about this, she says if it's too much we can cancel this whole thing. But it also makes me feel like shit going back on this. I also know that at some point, I'll probably need this as well, just like she does.

I don't know if this will pass. I don't know if, when she finally has sex with him, it'll make me feel worse or if it'll just be like "oh, that wasn't that bad".

Please tell me I'm dumb. I don't know what to do.